Field of the Invention
The present invention relates to a touch screen, a touch panel equipped with the touch screen, a display and electronic equipment equipped with the touch panel.
Description of the Background Art
A touch panel is a device to detect touch of a pointing body such as a finger and to identify a position coordinate of the touched position on the touch panel, and is receiving attention as one of excellent user interface means. At present, there are various types of touch panels commercially available such as a resistive film type and an electrostatic capacitance type. In general, a touch panel is equipped with a touch screen in which a touch sensor (a sensor for detecting touch) is incorporated, and is equipped with a detection device to identify a position coordinate of a position of the touch, based on a signal input from the touch screen.
As one of electrostatic capacitance touch panels, there is a projected capacitive touch panel (for example, see Japanese Patent Application Laid-Open No. 2012-103761). In a projected capacitive touch panel as described in Japanese Patent Application Laid-Open No. 2012-103761, even if a front surface side of the touch screen having a built-in touch sensor is covered with a protective plate such as a glass plate having a thickness of about several millimeters, touch can be detected. The projected capacitive touch panel is excellent in toughness because it is possible to dispose the protective plate on the front surface side of the touch screen. In addition, even when a user touches with a glove on, the touch can be detected. Further, the touch panel has no movable parts, and therefore has a long service life.
The projected capacitive touch panel is equipped with, as detection wirings for detecting a capacitance for example, a first series of conductor elements formed on a thin dielectric film and a second series of conductor elements formed on the first series of conductor elements with an insulating film therebetween (see Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. H9-511086 (1997), for example). The conductor elements form a plurality of intersection points without electrically touching with each other. In the configuration as described in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. H9-511086 (1997), a detection circuit detects capacitances formed between a pointing body such as a finger and the first series of conductor elements and the second series of conductor elements, which are the detection wirings; thus, the position coordinate of the position which the pointing body touches is identified. The above-described method of detecting a position coordinate is generally called a self-capacitance detection method.
Alternatively, there is a method of identifying the position coordinate of the touched position by, for example, detecting a change in an electric field, in other words, a mutual capacitance between a plurality of row wirings extendingly provided in a row direction to constitute a first electrode and a plurality of column wirings extendingly provided in a column direction to constitute a second electrode (see Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-526831, for example). This detection method is generally called a mutual capacitance detection method.
In any of the above self-capacitance type and mutual capacitance type, there is generally employed a method in which, when a plane area (detection cell) separated in a lattice shape by the row wirings and the column wirings is touched by a pointing body such as a finger, a position coordinate of the touched position is identified based on a balance between a detection value for the touched detection cell (sensor block) and a detection value for a detection cell in a vicinity of the sensor block.
Recently, there is realized a configuration in which metal having a low resistance is used to form a mesh as detection wirings and in which, by making use of a property of having a resistance lower than transparent electrodes such as ITO (Indium Tin Oxide), lead-out wirings to be connected to each terminal of the row wirings and the column wiring are connected to only terminal parts on one side of the row wirings and the column wirings (see Japanese Patent Application Laid-Open No. 2010-61502, for example).
There is a problem in such a configuration as described in Japanese Patent Application Laid-Open No. 2010-61502 that the lead-out wirings are connected to only the terminal parts on one side of each of the row wirings and each of the column wirings. The problem is that, when a pointing body (conductor) such as a finger coming close to the touch panel generates an electrostatic discharge, an electric charge is likely to accumulate on the other sides (the sides to which no lead-out wirings are connected) of the each of the row wirings and the each of the column wirings; therefore breakdown is likely to occur between the row-direction wiring and the column-direction wiring on the other sides.